Virulence factor activity relationships for hepatitis E and Cryptosporidium

Abstract

The hepatitis E virus and Cryptosporidium are waterborne pathogens, each consisting of distinct taxa, genotypes and isolates that infect humans, nonhuman animal species or both. Some are associated with disease, others are not. Factors contributing to disease are extremely complicated, possibly involving differences in one or more traits associated with an organism's taxon, genotype or isolate and its infectious dose, and age or condition, as well as the host's physiology and immune status. Potential virulence factors have not yet been identified for HEV.Putative virulence factors for Cryptosporidium might be found in recently recognized genes involved in processes such as excystation, adherence to host cells, invasion, intracellular maintenance and host cell destruction.

Cryptosporidium Pathogenicity and Virulence

“…Various host factors, including age, sex, and the status of the immune system, affect the outcome of the hostparasite interaction (13). In addition, the genotypic and phenotypic characteristics of the parasite define intrinsic diversity in isolate pathogenicity and virulence (14). Therefore, an integrated view of microbial pathogenesis and virulence accounting for the contribution of both host and pathogen factors and accommodating a spectrum of host-pathogen interactions provides a more accurate perspective (10,12).…”

“…Virulence factors are considered to be the processes and substances by which the parasite initiates and maintains disease in the host; these factors can affect the host at any time during the life cycle from the time when the parasite enters the body until it is killed or completes the cycle and exits the host (14). To date, Cryptosporidium-specific virulence factors have not been characterized to the point of unequivocally establishing their roles in causing damage to the host or proving that their deletion or inactivation results in a decrease of disease severity (13).…”

“…Putative virulence factors for Cryptosporidium have been identified as genes involved in the initial interaction processes of Cryptosporidium oocysts and sporozoites with host epithelial cells, including excystation, gliding motility, attachment, invasion, parasitophorous vacuole formation, intracellular maintenance, and host cell damage (14,133).…”